#include <stdio.h>

int main() {
	int n, m, i = 0;

	while (scanf("%d%d", &m, &n) != EOF) {

		//printf("# %d:\n", ++i);
		if (m * n % 2 != 0)
			printf("%d.41\n", m * n);
		else
			printf("%d.00\n", m * n);
	}
	return 0;
}